Oil well pump



C. L. ENGLISH OIL WELL PUMP July 5, 1960 7 Sheets-Sheet 2 Filed Oct. 9,1959 INVENTOR. Char/es L. English BY WWW A TTOPNE Y July 5, 1960 FiledOct. 9, 1959 C. L. ENGLISH OIL WELL PUMP 7 Sheets-Sheet s INVENTOR.Char/es L. Eng/fab A TTOP/VE Y July 5, 1960 Filed Oct. 9, 1959 C. L.ENGLISH OIL WELL PUMP FIEL-JU ,7 Sheets-Sheet 4 F 1 EEL- 1 INVENTOR..

CHAQLE'S L, EA/qL/"s ATTOP/VE-Y 7 Sheets-Sheet 5 mmvroa CHARLES L.EA/qLi'sH BY %"7% ATTOR C; LENGLISH I OIL WELL PUMP July 5, 1960 FiledQ01. '9, 1959 United States Patent OIL WELL PUMP Charles L. English,2204 E. 25th Place, Tulsa, Okla.

Filed Oct. 9, 1959, Ser. No. 845,571

32 Claims. (Cl. 103-46) This invention relates to improvements in fluidoperated pumping units of the type used below the surface in pumping oilwells. This is a continuation-in-part of applicants co pendingapplication entitled Oil Well Pump, filed October 9, 1957, Ser. No.689,181, now abandoned.

As it is well known in the oil producing industry, more and more wellsare being pumped by subsurface hydraulic or fluid actuated pumpingunits. The most popular present day subsurface hydraulic pump unitcomprises a substantially single acting pump powered by a hydraulicmotor, with the hydraulic motor receiving its motive force from highpressure oil pumped down the well to the motor. In general, thehydraulic motor comprises a differential area piston having its smallerend continuously exposed to high pressure power fluid, and a main valvein the piston for controlling the flow of power fluid to the larger endof the piston, whereby the piston is reciprocated to operate the pumpingunit. The main valve is in turn controlled by a pilot valve, with thepilot valve usually being carried by the piston and mechanically shiftedby the piston to open one or more ports and hydraulically shift the mainvalve. The pilot valve must be moved a substantial distance to controlthe flow of high pressure fluid to and from the main valve for thehydraulic operation of the main valve. As a result, the pilot and/ormain valves will be moved 01f center in the event the piston does notcomplete its stroke for some reason or other, or the valves partiallyshift by gravity when the unit is shunt down; whereupon the main valvewill be stuck in an inoperative position and can not be shifted untilthe unit is removed from the well. Present day pumps also experiencedifiiculty in operating at a desirably slow rate of speed on the workingstroke, as well as over an extended speed range and still not be tornapart when the pump encounters gas in the fluid being produced.Generally speaking, when gas is encountered, the resistance to thereturn stroke of the pumping unit is greatly reduced and the hydraulicmotor is moved on a return stroke with an excessive speed to literallytear the pumping unit apart.

The present invention contemplates a subsurface fluid operated pumpingunit having a control for the power fluid introduced into the motor ofthe unit for the return stroke, whereby the return stroke will beaccomplished at an acceptable speed at substantially any operatingcondition encountered. The present invention also contemplates the useof a single valve in such a pumping unit which will be operated throughthe major portion of its movement by hydraulic forces and will bemechanically unseated by a minute movement of the motor piston. Thevalve is so constructed and arranged as to automatically move to one ofits seats, such as the seat associated with a power stroke of thepumping unit, unless the valve is either completely on its opposite seator is just completing a power stroke, whereby the motor will not becomestuck or inoperative when the motor has been shut down for a period oftime, or when the motor piston does not complete a particular stroke.

An important object of this invention is to provide a fluid operatedpumping unit which may be operated as slow as desired, and yet may beoperated through a substantial speed range.

Another object of this invention is to provide a fluid motor having avalve which is thrown hydraulically upon being unseated mechanically,and, further, to minimize thae1 mechanical movement required foroperating the v ve.

A further object of this invention is to provide a fluid operatedpumping unit which may be operated effectively in gaseous wells.

Another object of this invention is to provide a fluid operated pumpingunit wherein the control valve for the motor is shifted into a positionfor a particular stroke of the unit, unless the valve is on its oppositeseat or the unit is just completing the particular stroke.

Another object of this invention is to provide a fluid operated pumpingunit wherein the power fluid is directed through the motor piston andthe velocity of the power fluid is controlled for a controlled returnstroke of the unit.

A still further object of this invention is to provide a fluid operatedpumping unit which will produce a minimum fluctuation of power fluidpressure during throwing of the valve. A

Other objects and advantages of the invention will be evident from thefollowing detailed description, when read in conjunction with theaccompanying drawings which illustrate my invention.

In the drawings:

Figure 1 is a vertical sectional view through a complete pumping unitconstructed in accordance with this invention.

Figure 2 is a sectional view as taken along lines 2-2 of Fig. 1.

Figure 3 is a sectional view as taken along lines 3--3 of Fig. 1.

Figure 4 is another sectional view as taken along lines 4--4 of Fig. l.

Figure 5 is a schematic sectional view of the motor illustrating theseated position of the valve for a power stroke of the pumping unit. I

Figure 6 is another schematic sectional view of the motor illustratingthe operation of the motor at the end of -the'power stroke. 7

'Figure 7 is a view similar to Fig. 6, illustrating a further shiftingof the valve.

Figure 8 is another schematic sectional view of the motor illustratingthe seating of the valve for a return stroke of the pumping unit.

Figure 9 is still another schematic sectional view of the motorillustrating the unseating of the valve at the lower end or completionof the return stroke.

Figure 10 is a vertical sectional view through the upper end portion ofa modified pumping unit constructed in accordance with this inventionillustrating a tubular type of valve, and with the valve in position fora power or upstroke of the unit.

Figure 11 is a vertical sectional view of the piston and valve shown inFig. 10, with the valve shown in position for a return or down stroke ofthe unit.

Figure 12 is a vertical sectional view through a modified pumping unitsimilar to the unit shown in Figs. 10 and 11 but illustrating aconstruction for controlling the force required to unseat the valve fromthe high pressure seat.

Figure 13 is a vertical sectional view of the valve and piston shown inFig. 12 and taken at right angles to Fig. 12.

Figure 14 is a vertical seetional view through the upper portion ofanother modified pumping unit illustrating the Patented July 5, 1960.

installation of the valve in the cylinder head, rather than in thepiston as in the previous embodiments, and with the valve shown inelevation.

Figure 15 is a vertical sectional view through the valve and cylinderhead shown in Fig. 14 and illustrating an opposite position of thevalve.

Figure 16 is a vertical sectional view through still an other modifiedembodiment of this invention.

Figure 17 is a vertical sectional view of the piston and valve shown inFig. 16, illustrating the valve in an opposite position.

Referring to the drawings in detail, and particularly Figs. 1 through 4,reference character generally designates the pumping unit which includesa motor cylinder 12 and a pump cylinder 14 threadedly secured in theopposite ends of a middle plug'16. -It will be observed that thecylinders 12 and 14 are arranged in tandem relation for positioning ofthe pump 10 in a well bore (not shown) in the usual manner. The middleplug 12 has a fluid inlet 18 in one side thereof for continuouslydirecting high pressure power fluid to the lower end of the motorcylinder 12, and a fluid outlet 20 in the opposite side for thedischarge of fluid from the pump cylinder 14. It will be understood thatthe inlet 18 and outlet 20 will be connected through suitablepassageways and conduits' (not shown) to the top of the well in theusual manner, whereby high pressure power fluid may be supplied to theinlet 18 and the pumped fluid recovered from the outlet 20.

A suitable head 22 is secured on the upper end of the motor cylinder 12,and a suitable shoe 24 is secured to the lower end of the pump cylinder14. The shoe 24 contains a standing valve 26 of any desired type, and aspider or stop 28 is secured between the valve 26 and the lower end-ofthe -cylinder 14 to limit the upward movement of the valve 26. Thestanding valve 26 operates in the usual manner to open in an upwarddirection when a suction is induced in the lower end of the cylinder 14and to seat against the seat 39 when the pressure 'in the lower end ofthe pump cylinder 14 is greater than the pressure below the valve, thatis, well pressure.

A fluid operated motor piston assembly 32 is reciprocally disposed inthe motor cylinder 12 and is connected through a hollow middleorconnecting rod 34 to a pump piston 36 in the pump cylinder 14. Theconnecting rod 34 extends through a suitable packing gland 38 in themiddle plug 16, whereby fluid in the cylinders 12 and 14 will beseparated, and the middle plug 16 will form the adjacent heads for thecylinders 12 and 14. The pump piston 36 has a series of suitable pistonrings 40 on the outer periphery thereof in sliding and sealingengagement with the inner periphery of the cylinder 14, and acombination valve seat and guide 42 for a traveling valve 44. The valve44 may be of any suitable type to control the flow of fluid through thebore 46 extending vertically through the piston 36. The bore .6communicates with the interior of the hollow connecting rod 34 through achamber 48, whereby fluid flowing downwardly through the connecting rod34 will be directed into the pump cylinder 14 above the pump piston 36,as will be more fully hereinafter set forth.

The motor piston assembly 32 comprises a piston member 50 havinga seriesof suitable piston rings 52 on the outer periphery thereof in slidingand sealing engagement with the inner periphery of the motor cylinder12. A tubular extension 54 is threadedly'secured to the'lower end of thepiston member 50 and is in turn threadedly connected to the upper end ofthe hollow connecting rod 34. An elongated valve chamber 56 is providedin the central portion of the piston member 50 and extends in adirection parallel to the reciprocal movement of the piston member 50 toslidingly receive a valve member 58. High and low pressure valve seats60 and 62, respectively, are secured in the piston member '50 at theopposite ends of the valve chamber 56 to receive the seating areas 64and 66, respectively, of the valve 58, as will be more fully hereinafterset forth. It will also be observed that the valve 58 has a cylindricalextension or choke 68 on each end thereof of reduced diameter and of asize to enter the respective valve seats 60 and 62 when the valve 58 isseated on the respective seat. Although it will be explained more indetail below in connection with the operation of the unit, it may alsobe noted here that the valve 58 is of such a size, and the valve seats68 and 62 are so spaced, that the upper extension 68 will still bewithin the upper valve seat 60 when the lower extension 68 enters thelower valve seat 62, and vice versa, during reciprocation of the valve58.

The valve 58 also has a head portion 70 slidingly disposed in asecondary valve chamber 72 below and in line with the main valve chamber56. A neck 74 extends upwardly from the head portion 70 to the lowerextension 68 of the valve 58. For convenience in manufacture, I preferto form the head portion 70 and neck 74 separately from the remainingportion of the valve 58. It will be understood however, that thesemembers may be formed as an integral unit, since they operate as a unitin controlling the movement of the piston assembly 32. The neck 74 is ofa size to extend through the lower valve seat 62 with substantialclearance around the neck 74 when the valve 58 is in its upper positionas illustrated in Fig. 1.

Opposed slots 76 (Figs. 1 and 3) are provided in the walls of thesecondary valve chamber 72 at the lower end of the chamber to looselyreceive a cross-member 78 of a valve actuating harness 80. The harness80 loosely surrounds the piston extension 54 and may thus move'up anddown over the extension 54; however, the harness 80 will normally beretained in its lower position, as shown, by gravity. It will also beobserved that the slots 76 are of a size to provide constantcommunication between the lower end portion of the motor cylinder 12 andthe lower end of the secondary valve chamber 72, whereby high pressurepower fluid is constantly exposed to the lower end face of the valvehead portion 70.

As illustrated in Fig. 2, a series of circumferentially spacedtransverse ports 82 extend through the piston member 50 slightly belowthe lower piston ring 52 to provide communication between the motorcylinder 12 below the piston member 50 and the valve chamber 56 slightlybelow the upper, high pressure valve seat 60. The ports 82 are thusutilized to provide a constant supply of high pressure power fluid tothe upper end of the valve chamber 56, as will be more fully hereinafterset forth.

A value actuating sleeve 84 extends through a bushing 86 in the upperend of the piston member '50 in line with the valve member 58. The lowerend of the sleeve 84 extends into the valve seat 60 to provide apassageway from the upper end of the valve chamber 56 to the upperportion of the motor cylinder 12 above the piston member 50. A helicalcompression spring 88 is anchored to the valve seat 60 and a flange 90on the sleeve 84 to urge the sleeve 84 upwardly and in a direction outof the piston member 58. It will be observed that the flange 90 alsoserves as a stop against the bushing 86 to limit the outward movement ofthe sleeve 84. The outer end 92 of the sleeve :84 is squared 011 withrespect to the bottom face of the head 22; that is, the upper end 92 ofthe sleeve 84 is formed on the same plane as the bottom face of the head22, whereby the sleeve 84 will closely contact the bottom face of thehead 22 around the entire periphery of the sleeve when the sleeveismoved upwardly against the head. The inner diameter of the sleeve 84is substantially less than the inner diameter of the seat 60 and thecombined diameters of the ports 82, whereby the sleeve 84 will form anorifice for controlling the high pressure fluid directed through theports 82 and valve seat 60 toward the upper end of the piston member 50.It should be further noted that the clearance around the lower end ofthe sleeve 84 (between the sleeve 84 and the inner periphery of thevalve seat 60) is less than the clearance between the upper valveextension 68 and the inner periphery of the valve seat 60, whereby fluidintroduced to the valve seat 60 will flow around the upper extension 68with less resistance than it will flow around the sleeve 84. It isfurther preferred that notches 94 be cut in the lower end of the sleeve84 to provide passageways for fluid escaping around the upper valveextension 68 when the sleeve 84 is in contact with the valve, as will bemore fully hereinafter set forth. 3

A tubular insert 96 is threaded into the upper end of the piston member50 to form a plurality of exhaust passageways 98 from the upper face ofthe piston member 50 to a point approximately even with the upper valveseat 60. It will be observed that the bushing 86 receiving the sleeve 84is formed by an inner portion of the insert 96. A plurality of verticalbores 100 are formed lengthwise in the piston member 50 outwardly of thevalve chambers 56 (see also Fig. 2) to form continuations of the exhaustpassageways 98. The lower ends of the bores 100 communicate with achamber 102 which is formed between the lower end of the valve chamber56 and the lower ends of the bores 100. The chamber 102 is locateddirectly above the lower, low pressure seat 62, whereby exhaust fluidmay flow from the bores 100 through the chamber 102 and the lower valveseat 62 when the valve 58 is in its upper position as illustrated.Additional bores 104 are formed vertically in the piston extension 54 onopposite sides of the secondary valve chamber 72 to direct theexhausting fiuid downwardly from the seat 62 to a chamber 106 formed inthe lower end portion of the piston extension 54 directly above theupper end of the hollow connecting rod 34. Thus, when the valve 58 isofl of the seat 62, communication is established from the top of thepiston member 50 through the passageways 98, bores 100, chamber 102,seat 62, bores 104 and chamber 106 to the interior of the hollowconnecting rod 34.

Operation As previously indicated, high pressure power fluid isconstantly directed through the inlet 18 into the lower end of the motorcylinder 12 for operation of the pumping unit 10. The power fluid in thelower end of the motor cylinder 12 acts on all of the exposed areas ofthe piston extension 54 and the lower exposed face of the piston member50 to constantly urge the piston assembly 32 in an upward direction.Simultaneously, high pressure fluid is directed through the slots 76into the lower end of the secondary valve chamber 72 to act in an upwarddirection on the lower end of the valve head portion 70, and through theports 82 to act on some portion of the upper end of the valve 58.

In general, the operation of the pumping unit is such that when thevalve 58 is in its upper position as illustrated in Fig. 1, the upperend of the piston member 50 is exposed to a pressure lower than thepower fluid pressure through the various exhaust passageways and boresdescribed above and the hollow connecting rod 34 through the upper endof the pump cylinder 14. In this position of the valve 58, the net forceimposed on the piston assembly 32 will be in an upward direction toraise the motor piston assembly 32 and the pump piston 36. As the pumppiston 36 is raised, the traveling valve 44 is closed by fluid in theupper portion of the pump cylinder 14 to provide a suction in the lowerend of the cylinder 14. Well fluid surrounding the pump unit 10 is thendrawn upwardly through the standing valve seat 30 into the lower end ofthe cylinder 14. Simultaneously, of course, fluid in the upper end ofthe cylinder 14 is forced through the outlet 20 and upwardly through thewell to the surface where it may be recovered. Thefluid being raised anddirected through the outlet 20 will therefore be a combination of wellfluid drawn into the cylinder 14 on a previous up stroke, and powerfluid exhausting from above the motor piston member 50 downwardlythrough the connecting rod 34 and into the upper portion of the pumpcylinder 14.

1 At the end of the up or power stroke, the sleeve 84 contacts the head22 to mechanically unseat the valve 58, and the valve 58 is then shiftedhydraulically onto the lower seat 62, as will be explained in moredetail below. It will then be observed'that communication is establishedfrom the ports 82 to the interior of the seat 60, whereby power fluid isdirected through the ports 82, seat 60 and sleeve 84 into the upper endof the motor cylinder 12 to act in a downward direction on the upper endof the piston member 50. Simultaneously, the lower seating portion 66 ofthe valve 58, in combination with the valve seat 62, preventscommunication between the exhaust bores 100 and the exhaust bores 104.In this condition, power fluid will be acting on the piston extension 54and the lower face of the piston member 50, as well as the upper end ofthe piston member 50. It will be observed, however, that the area of theupper face of the piston member 50 is greater than the exposed area ofthe lower face of the piston member 50 and the extension 54 by an areaequal to the cross-sectional area of the hollow connecting rod 34.Therefore, the piston assembly 32 is what is commonly known in the artas a differential piston, and, assuming the pressure of the fluid in theupper end of the motor cylinder 12 is substantially equal to thepressure of the fluid in the lower portion of the motor cylinder 12, thenet force on the piston assembly 32 will be in a downward direction tomove the pump unit 10 on a down stroke.

As the pump piston 36 is moved downwardly, the standing valve 26 isclosed by an increase in pressure in the lower end of the pump cylinder14 compared with the pressure of fluid below the shoe 24, and thetraveling valve 44 is opened by reason of a greater pressure in thelower end of the pump cylinder 14 than the pressure in the upper portionof the cylinder 14. Thus, fluid in the lower portion of the cylinder 14will be moved through the valve seat 42 and passageways 46 into theupper portion of the cylinder above the pump piston 36. It may also benoted that a volume of fluid equal to the volume occupied by theconnecting rod 34 will be displaced through the outlet 20 and upwardlythrough the well. However, this displaced fluid is small compared to thevolume of fluid displaced on the up stroke, hence the down stroke may beconsidered as a return or non-working stroke and the pump unit may beconsidered as single acting.

At the end of the down stroke, the harness contacts shoulders 16a in themiddle plug 16 to raise the harness 80 (with respect to the pistonassembly 32) into contact with the head portion 70 of the valve 58. Thisoperation mechanically unseats the valve 58 from the lower seat 62, andthe valve 58 is then thrown hydraulically back to the upper seat 60, aswill be explained in more detail below. The up stroke of the pumpingunit is then effected in the same manner as previously described.

The detailed operation of the valve 58 and the various positions of thevalve are best illustrated in Figs. 5 through 9. The position of thevalve 58 for an up stroke of the pumping unit is shown in Fig. 5. Itwill be observed that the upper seating area 64 of the valve is incontact with the upper, high pressure seat 60 to prevent the flow ofhigh pressure power fluid to the upper end of the motor cylinder 12.Also, the lower seating area 66 of the valve is above the low pressureseat 62, and the lower valve extension 68 is withdrawn from the interiorof the seat 62 to open the exhaust passageway from the upper end of themotor cylinder 12 to the hollow con- .necting rod 34. It may be furthernoted that the. neck 74 of the valve head portion 70 is substantiallysmaller in diameter than the inner diameter of the lower seat 62 toprovide substantially unrestricted flow of the exhaust fluid through thevalve seat 62.

The valve 58 is held on its upper seat by a combination of hydraulicforces which result in a net upward force. In detail, the hydraulicforce exerted by the high pressure power fluid on the lower end of thehead portion 70, plus the force exerted by the exhaust fluid pressure onthe lower face of the main body portion of the valve 58 is greater thanthe force exerted by the exhaust fluid pres sure on the upper end of theupper extension 68 and approximately /2 of the area of the seat 64, plusthe high pressure fluid exerted downwardly on the exposed area of thevalve 58 between the middle of the valve seating area 64 and the outerperiphery of the valve, plus the lower pressure fluid exerted downwardlyon the crosssectional area of the head portion 70.

Near the end of the up stroke, the upper end 92 of the sleeve 84contacts the lower face of the upper motor cylinder head 22 to providean upward movement of the piston member 50 over the sleeve 84. As soonas the upper extension 68 of the valve 58 contacts the lower end of thesleeve 84 (see Fig. 6), the valve 58 is unseated from the upper seat 60,by virtue of the continued upward movement of the piston member 50. Uponunseating of the valve 58 from the valve seat 60, high pressure fluidleaks around the upper extension 68 and through the notches 94 to exertan increased pressure on the upper end of the upper extension 68. Aspreviously indicated, the clearance around the upper extension 68 isgreater than the clearance around the lower end of the sleeve 84. Also,the mating faces of the upper end 92 of the sleeve 84 and the lower faceof the head 22 restricts the flow of fluid upwardly around the upper endof the sleeve 84 to such an extent that high pressure fluid leakingaround the upper extension 68 will be substantially confined within thesleeve 84 to provide a higher pressure on the upper end of the upperextension 68 than exists in the lower end of the valve chamber 56, whichlast-mentioned pressure acts upwardly on the lower end of the valve 58.It should also be noted that the high pressure fluid which does leakpast the sleeve 84 is exhausted through the lower seat 62, even afterthe lower extension 68 enters the lower seat 62, since the clearancebetween the lower extension and lower valve seat is greater than theclearance between the upper extension and upper valve seat. Thisincrease in pressure above the upper extension 68 is sufiicient toovercome the previously described upwardly acting hydraulic forces andprovide a downward movement of the valve member 58. It will be furtherobserved that the upper extension 68 remains in the valve seat 60 untilafter the lower extension 68 enters the lower valve seat 62 to seriouslyrestrict the flow of high pressure fluid to the sleeve 84. In addition,the sleeve 84 remains in contact with the upper head 22 until after thevalve 58 is completely shifted to the lower seat (Figs. 7 and 8).Therefore, the sleeve 84 prevents a substantial supply of high pressurefluid being directed to the upper end of the motor cylinder 12 until theexhaust from the upper end of the motor cylinder is stopped by reason ofthe valve 58 being on the valve seat 62.

The leakage around the upper valve extension 68 compared with theleakage around the lower end of the sleeve 84 and through the upper endof the sleeve 84 during the unseating operation may be so adjusted thatthe valve 58 will be thrown hydraulically immediately upon beingunseated mechanically by the sleeve 84. With this arrangement, theupward movement of the motor piston assembly 32 will be slowly reversedto prevent damage by the piston assembly 32 contacting the upper head 22and to allow suflicient time for the standing valve 26 of the pump unit"to become seated for the subsequent down stroke.

With the valve-58in its lowerposition asshownin Fig. 1

8, the ports 82 will be in communication with the sleeve 84 to directhigh pressure power fluid against the upper cylinder head 22 which leaksaround the upper end of the sleeve and tends to move the piston assembly32 down; As-soon as the sleeve 84 is removed from the head 22, highpressure fluid is supplied to the upper end of the motor cylinder atincreased velocity to increase the speed of the down stroke.

' In its lower position, the valve 58 is urged downwardly by the actionof high pressure power fluid contacting the entire upper area of thevalve, including the upper extension 68, as well as the pressure of theexhausting fluid acting on the upper end of the head portion 70. Thesedownwardly acting forces are greater than the force obtained by theaction of the high pressure power fluid on the lower end of the headportion 70 and the high pressure power fluid acting on the area of thevalve 58 between approximately the center of the lower seating area 66and the outer periphery of the valve, plus the lower pressure exhaustfluid acting upwardly on the remainder of the lower end of the valve 58.It may also be observed that the valve 58 will stay on this lower seatduring the down stroke, regardless of the loss of load on the pump endof the unit. The exhaust pressure acts on the upper end of the headportion '71 and the lower extension 68 out to approximately the centerof the lower seating area 66 and these forces substantially cancel out,regardless of the exhaust pressure.

Near the end of the down or return stroke of the pumping unit 10, theharness 89 contacts the middle plug .16 and the lower end of the headportion 70 to unseat the valve 58 from the lower seat 62 as shown inFig. 9. Immediately upon this unseating movement, the entire lowerseating area 66 of the valve is exposed to the high pressure powerfluid. This addition to the upwardly acting hydraulic forces issuflicient to overcome the downwardly acting hydraulic forces and movethe valve 58 upwardly through the valve chamber 56 and seat the valve onthe upper seat 60. It will thus be apparent that the upward movement ofthe valve 58 is initiated by a minute downward movement of the motorpiston assembly 32 when the harness contacts the middle plug 16.Although the motor piston assembly 32 will continue moving downwardly byits own momentum upon shifting of the valve 58, the high pressure fluidin the lower end of the motor cylinder 12 will be prevented from furtherleakage through the upper valve seat 60 to provide a cushioning effectand tend to prevent the lower end of the piston assembly 32 fromcontacting the middle plug. In addition, I prefer to provide a dash potaction in the lower end of the motor cylinder 14 to bring the motorpiston assembly 32 to a rather slow stop at the end of a downwardmovement and to retard the initial portion of the up stroke of the unit.This dash pot may take any suitable form, such as a cylindrical cavity(Fig. 1) formed in the upper end of the middle plug 16 of a size toloosely receive the lower end of the motor piston extension 54. The sidewalls of the cavity 110 and the lower end of the piston extension 54 maybe tapered as desired to provide the necessary dash pot action. Withthis delay in reversal of the pumping unit 10, the traveling valve 44will have sufficient time to seat itself on the seat 42 prior to theoncoming up stroke to prevent damage to the traveling valve andassociated parts.

When the valve 58 has been moved upwardly to such a position that theupper valve extension 68 enters the upper seat, as illustrated in Fig.6, the ilow of high pressure power fluid into .the exhaust passageways98 etc. is restricted, thereby reducing the upward force on the lowerend face of the valve. Therefore, to assure a final seating on the upperseat 60, the cross-sectional area of the head portion 70 (being urged upby high pressure power fluid) must be greater than the cross-sectionalarea of the .main body portion of the valve 58 less the somecross-sectional area of .the upper extension 68, which lastmentionedarea is being forced down by the high pressure power fluid.

One of the important features of the present invention is the provisionof an orifice in the power fluid passageway leading to the upper, largerend of the motor piston assembly 32 to control the down, return strokeof the pumping unit. The inner diameter of the sleeve 84 is made of sucha size, as compared to the size of the seat 60 and ports 82, to providean orifice downstream of the valve 58. The cross-sectional area of thisorifice should .be no more than fifty percent as large as thecross-sectional area of either the seat 60 or the ports 82, and ispreferably only twelve to fifteen percent as large as either of thelast-mentioned areas. By positioning the orifice downstream of thevalve, the orifice will tend to retain a pressure on the upper end ofthe valve 58, particularly on the down stroke to retain the valve in itslower position. Also, the orifice will control the amount of highpressure power fluid introduced into the upper end of the motor cylinder12, whereby the speed of the down or return stroke of the pumping unitmay be subject to control. As it is well known in the art, the changesin velocity of a liquid flowing through the sleeve 84 will besubstantially equal to only the square root of the changes in pressureof the high pressure power fluid upstream of the sleeve. Therefore, whenthe pressure of the power fluid is increased .to increase the speed ofoperation of the pumping unit 10, the speed of the down stroke of theunit will be increased a substantially lesser extent than that of the upstroke. This feature increases in importance when the most desiredoperation of the pumping unit is analyzed. The cross-sectional areas ofthe piston assembly 3 2 and the connecting rod 34 are such to provide arelatively slow up stroke for the unit as compared .to the down stroke,since the-up stroke is the working stroke and the down stroke is anonworking stroke. This relative movement is also desirable to minimizethe velocity of well fluid sucked into the lower end of the pumpcylinder 14:. Thus, at a normal operating speed, the down stroke will beaccomplished substantially faster than the up stroke. And, if the speedof the down stroke is increased substantially the same amount as thespeed of the up stroke upon an increase in pressure of the power fluid,as occurs when no orifice is present, the operating range of the pumpingunit is seriously limited.

Another feature of note in the present invention is the capability ofthe unit for operation at a speed as slow as desired. This advantage ismade possible principally by the minimum loss of power fluid in shiftingthe valve 58, and the minute piston movement required to unseat thevalve at the opposite ends of the piston movement to subject the valve58 to hydraulic forces for a complete shifting of the valve. Since onlya minute mechanical movement is required to initiate shifting of thevalve 58, it is a practical impossibility to stick the valve 58 in aninoperative position by only a partial mechanical movement, as inpresent day pumps utilizing a pilot and main valve as describedpreviously. As to loss of power fluid in shifting the valve 58, it willbe observed that as the valve is shifted in either direction, theleading ex tension 68 enters the respective seat 60 or 62 at an earlypoint in the valve movement and restricts the amount of leakage throughthe seat until the valve is seated.

Still another feature of note in the present invention is the tendencyof the valve 58 to move to one of the valve seats under certainconditions. In the preferred form, the valve 58 moves to its upper seat,unless the valve is either on its lower seat or the pumping unit is justcompleting an up stroke. The movement of the valve 58 is, of course,controlled by the relative areas of the valve and the porting throughthe motor piston assembly 32 which exposes the various areas to high andlow pressures. These factors are so controlled to provide a net upwardforce on the valve, unless the valve is in either of the two positionspreviously described. It will be observed in Figs. 5 through 9 that inevery position of the valve 58, except when the valve is on the lowerseat or the pumping unit is completing an up stroke, the entire top ofthe valve is exposed to high pressure power fluid tending to force thevalve down, and the lower end of the head portion 7 0 and the areabetween the outer periphery of the valve and the lower extension 68, oronly the lower end of the head portion 70 and the upper end of the valveless the upper extension 68 are exposed to high pressure fluid tendingto force the valve up. Therefore, the cross-sectional area of the headportion 70 should be greater than the cross-sectional area of the upperextension 68, as well as greater than the cross-sectional area of themain body portion of the valve less the cross-sectional area of theupper extension 68 to assure that the valve will be moved up when, forexample, the pumping unit is first run in a well or is started after aperiod of idleness. However, the crosssectional area of the head portion70 should be less than the cross-sectional area of the valve 58 in orderthat the valve will move to the lower seat under the conditions shown inFigs. 6 and 7 and will remain on the lower seat during the down stroke.

In constructing a valve in accordance with this invention, the variousareas exposed to power and exhaust fluid may be easily proportioned tomaintain the valve on either seat with an extremely small force,compared to present day valves. In practice, the hydraulic force holdingthe valve on either seat should be no greater than ten percent of thedifference between the power and exhaust fluid pressures, and preferablyless than five percent. This arrangement minimizes damage to the valveseats, and, of course, the force required to shift the valve, which inturn minimizes fluctuations in power fluid pressure when shifting thevalve.

' Embodiment of Figs. 10 amf 11 A modified embodiment of this inventionis illustrated in Figs. 10 and 11 and comprises a pumping unit 200constructed, in many respects, similar to the pumping unit 10 previouslydescribed. The pumping unit 200 may be easily constructed to utilize themotor cylinder 12 and pumping cylinder 14 interconnected in tandemrelation by the middle plug 16 in the same manner as in the pumping unit10. In this embodiment, a modified motor piston assembly, generallydesignated by reference character 202, is reciprocally disposed in themotor cylinder 12 for movement in response to power fluid introducedinto the motor cylinder through the inlet 18 in the middle plug 16. Thelower end of the motor piston assembly 202 is connected to the hollowconnecting rod 34 which extends through packing 38 in the middle plug 16into connection with a suitable pump plunger (not shown) 'disposedWithin the pump cylinder 14 in substantially the same manner as in thepumping unit 10, previously described.

The modified motor piston assembly 202 comprises a main tubular pistonmember 204 of a size to slidingly fit in the motor cylinder 12 andhaving suitable piston rings 206 around the outer periphery thereof toslidingly seal the main piston member 204 in the motor cylinder 12. Atubular extension 208 is threadedly secured on the lower end of thepiston member 204 and extends downwardly from the piston 204 intoconnection with the upper end of the hollow connecting rod 34 in anysuitable manner, such as by the use of threads 210. It will also benoted that the piston extension 208 is reduced'in diameter to providesubstantial clearance between the outer periphery of the extension 208and the inner periphery of the motor cylinder 12.

The upper end 212 of the piston member 204 is reduced in diameter andinternally threaded to receive'a tubular insert 214 which forms one endportion 216 of a valve chamber 218 in the motor piston assembly 202. Thelower end portion of the insert 214 is provided with ports 220 whichcorrespond with ports 222 in-the piston member 204 to providecommunication between the upper end portion of the motor cylinder 12 andthe valve chamber 218. A low pressure annular valve seat 224, having anupwardly facing annular seating area 226, is secured in the bore of thepiston member 204 between the lower end of the insert 214 and the upperend of another insert 228 positioned in the medial portion of the pistonmember 204. It will therefore be observed that the insert 228 forms themajor portion of the valve chamber 218 and communicates with the valvechamber portion 216 through the low pressurevalve seat 224. It may alsobe noted that the upper end portion 230 of the tubular insert 228 is ofa size to fit tightly within the bore of the piston member 204, whilethe main body portion 232 of the insert 228 is reduced in diameter toprovide an annular passageway 234 between the outer periphery of thevalve body portion 232 and the inner periphery of the piston member 204.The passageway 234 communicates with the low pressure valve seat 224-through ports 236 extending at an angle through the upper end portion230 of the insert 228.

The lower end 238 of the insert 228 is in contact with a high pressurevalve seat 240 having a downwardly facing annular seating area 242. Thevalve seat 240 is held between the lower end 238 of the insert 228 andthe upper end of the piston extension 208 and extends into the upper endof a bore 244 in the extension 208. Passageways 245 extend through theextension 208 around the bore 244 and communicate with the passageway234 in the piston member 204. A counterbore 246 is formed in the lowerend of the piston extension 208 to provide communication between thepassageways 245 and the upper end of the hollow connecting rod 34. Also,it will be observed that the bore 244 provides an extension of the valvechamber 218 and has its inner diameter increased in downwardly spacedrelation from'the seat 240 to provide a slightly enlarged portion 248 atthe lower end of the valve chamber 218. A slot 250 is extendedtransversely through the piston extension 208 to provide constantcommunication between the lower end portion 248 of the valve chamber 218and the lower end of the motor cylinder 12, whereby the high pressurepower fluid in the lower end portion of the motor cylinder 12 will be inconstant communication with the lower end portion of the valve chamber218 below the high pressure valve seat 240.

The valve mechanism is generally designated by reference character 252and is reciprocally disposed in the valve chamber 213 for controllingthe flow of fluid to and from the upper end portion of the motorcylinder 12. The valve mechanism 252 comprises a tubular main valve body254 having an extension 256 on the lower end thereof of a size to extendthrough the high pressure valve seat 240 with substantial clearancebetween the extension 256 and the inner periphery of the valve seat 240.The bore 258 extending longitudinally through the valve body 254communicates with the valve chamber 218 immediately above the valve seat240, through ports 260, and is open at the upper end of the valve body254 to provide a flow of high pressure power fluid through the valvechamber 218 upon opening of the valve seat 240, as will be described.

The medial portion of the valve body 254 is of a size to slidingly fitin the valve chamber 218, and the upper end or head portion 262 of thevalve body 254 is increased in diameter to slidingly fit in the enlargedupper end portion 216 of the valve chamber. The lower face 264 of thehead portion 262 is tapered downwardly and inwardly to mate with thesealing area 226 of the valve seat 224 in the lower position of thevalve body 254, as illustrated in Fig. 11. Immediately below the seatingarea 264, the valve body 254 is provided with a cylindrical portion 266of a size to provide a loose sliding tit 12 thereof in the low pressurevalve seat 224 to form a choke member and control flow of fluid throughthe valve seat 224 in intermediate positions of the valve body 254, aswill be described. That portion 268 of the valve body 254 between thechoke portion 266 and the main body portion of the valve is reduced indiameter to provide substantial clearance between the valve body and thevalve seat 224 when the valve is in its upper position as illustrated inFig. 10.

A ball member 270 is positioned in the valve chamber 2.18 below the highpressure valve seat 240 and is of a size to engage the seating area 242of the valve seat 240 as illustrated in Fig. 10. It will be apparentthat the ball 270 forms the lower valve head for the valve mechanism 252to alternately open and close the valve seat 240. The ball 270 may beformed as an integral part of the valve body 254, although I prefer toform the ball 270 separately from the valve body for economy ofmanufacture. In either of these constructions, the ball 270 will operateefficiently to open and close the valve seat 240 in the alternatepositions of the valve mechanism.

Another choke member 272 is positioned in the lower end portion 248 ofthe valve chamber and is of a size to substantially restrict the flow ofhigh pressure fluid from the inlet 250 into the valve chamber 218 whenin an upper position (not shown in the drawings). An extension 274 isformed on the upper end of the choke member 272 and is provided withcircumferentially spaced ears 276 which slidingly engage the walls ofthe valve chamber 218 above the enlarged portion 248 for guiding thechoke member 272 in its upward and downward movements. It will be notedthat the diameter of the extension 274 is substantially less than thediameter of the valve chamber 218 above the enlarged portion 248, suchthat the extension will provide no appreciable restriction to flow ofpower fluid from the inlet 250 into the valve chamber 218 when the chokemember 272 is in its lowermost position, as shown in both Figs. 10 and11.

In the pumping unit 200, the actuating means for mechanically moving thevalve mechanism 252 off of the valve seats 224 and 240 comprises asleeve 280 at the upper end of the motor piston assembly 202 slidinglyextending into the upper end portion 216 of the valve chamber 218. Thesleeve 280 is decreased in diameter at 282, and the upper end of theinsert 214 is provided with an inwardly extending flange portion 284 toengage the sleeve 280 in the upper position of the sleeve and preventthe sleeve from moving out of the valve chamber. Counterbores 286 and288 are provided in the lower end of the sleeve 280 and the upper end ofthe valve body head portion 262, respectively, to receive the oppositeends of a helical spring 290 which constantly urges the sleeve 280upwardly away from the valve body 254, as will be described. Also, apartial flange or shoulder 292 is formed on the lower face of the sleeve280 around the counterbore 286 to contact the upper face of the valvebody head portion 262 when the sleeve 280 is moved against the valvebody to permit the application of fluid pressure against the upper endof the valve head 262, as will be described. Finally, it may be notedthat the inner bore 294 through the sleeve 280 is substantially smallerin cross-sectional area than the bore 258 through the valve body 254 toprovide an orifice for the high pressure fluid being directed to theupper end portion of the motor cylinder 12, as will be described.

The valve actuating means at the lower end of the piston assembly 202comprises a cross bar 296 extending through the slot 250 in the pistonextension 208. The cross bar 296 is suitably connected (not shown) atits opposite ends to a ring 298 which forms a harness assembly forengaging the choke member 272 when the piston assembly approaches theend of the down stroke in substantially the same manner as the operationof the hartages 13 ness 30 previously described in connection With thepumping unit 10.

In operation of the pumping unit 200, the valve mechanism 252 will be inthe position shown in Fig. on the up stroke or power stroke of thepumping unit, and the valve mechanism will be in the position shown inFig. 11 on the down stroke or return stroke of the pumping unit.Referring first to Fig. 10, it will be noted that the high pressurepower fluid is constantly available at the inlet 18 and is dischargedinto the lower end portion of the motor cylinder 12 to react on thelower, smaller end portion of the piston assembly 202. This highpressure power fluid is also constantly available in the lower endportion of the valve chamber 218 through the inlet 250. On the up strokeof the unit, this power fluid is directed through the lower portion ofthe valve chamber 218 against the ball member 270 to hold the ballmember 270 on the seat 240, such that the high pressure power fluidcannot flow on upwardly through the valve chamber 218 to the upper endof the motor cylinder 12.

Fluid in the upper end portion of the motor cylinder 12 is exhaustedthrough the ports 222 and 220 into the upper end portion of the valvechamber 218. Since the valve seating area 264 is spaced upwardly abovethe low pressure seat 224, this exhausting fluid may flow on downwardlythrough the seat 224 around the valve body portion 268 and then throughthe annular exhaust passageway 234 and passageways 245 to the upper endof the hollow connecting rod 34. As described in connection with 'thepreferred embodiment illustrated in Figs. 1 through 9, this exhaustingpower fluid is combined with well fluid in the pump cylinder 14 and isdischarged through the outlet 20.

Near the end of the up stroke of the pumping unit 200, the upper end ofthe sleeve 280 contacts the lower face of the motor cylinder head 22;whereupon the insert 214 is telescoped upwardly over the sleeve 280.Upon continued upward movement of the piston assembly 202, the valvebody head 262 is brought into contact with the flange 292 on the lowerend of the sleeve 280. The sleeve 280 will therefore move the valve body254 relatively downward in the valve chamber 218 through physicalcontact and remove the ball member 270 olf the high pressure seat 240.The high pressure power fluid present in the lower end of the valvechamber 218 will therefore flow upwardly through the seat 240 andthrough the valve body 254 toward the upper end of the motor cylinder12. However, since the upper end of the sleeve 280 is in contact withthe motor cylinder head 22, this upwardly flowing high pressure fluid isprevented from escaping into the upper end of the motor cylinder 12 andreacting on the entire piston assembly 202. When the ball member 270- isremoved from the seat 240, the high pressure fluid in the valve body 254flows outwardly between the mating faces of the sleeve member 280 andthe upper head portion 262 of the valve body to provide a downwardlyacting force on the valve body 254 which moves the seating area264'toward the low pressure seat 224. It will also be noted that duringthe early stages of the downward movement of the valve body 254, thechoke portion 266 of the valve enters the low pressure valve seat 224and restricts flow of fluid from above the piston assembly 202downwardly through the valve seat 224. Therefore, a cushioning of theupward movement of the piston assembly is obtained and the minimum offluid will be lost through the valve chamber during shifting of thevalve. The seating area 264 will be fully seated on the valve seat 224even though the piston assembly 202 may start on the down stroke andremove the sleeve 280 from the cylinder head 22, since the innerdiameter of the seat 224 is larger than the outer diameter of theportion 254 of the valve mechanism. When the valve 254 is seated on theseat 224, all flow through the valve seat 224 is stopped and the valvewill be held on this seat in hydraulic forces.

As previously indicated, the down stroke position of the valve mechanismis illustrated in Fig. 11. It will be observed that in this position ofthe valve mechanism, the high pressure valve seat 240 is opened, suchthat the high pressure power fluid will flow upwardly through the valvebody 254 and through the sleeve member 280 into the upper end portion ofthe motor cylinder 12 to react on the upper, larger end of the pistonassembly 202. Since the upper end of the piston assembly 202 is largerthan the lower end of the piston assembly (by reason of the connectingrod 34) the net force reacting on the piston assembly 202 will force thepiston assembly 202 on a down stroke. It has already been noted that thevalve mechanism is in a closed position with respect to the low pressureseat 224 to prevent a discharge of fluid from the upper end of the motorcylinder 12 and into the connecting rod 34.

As the piston assembly 202 approaches the end of the down stroke, theharness ring 298 contacts the shoulder 16a of the middle plug 16 to movethe choke member 272 upwardly with respect to the valve chamber 218. Theball member 270 resting on the upper end of the choke member 272 istherefore also moved upwardly and into contact with the extension 256 ofthe valve body 254 to move the seating area 264 of the valve headportion 262 off the low pressure seat. As the valve 252 is unseated fromthe low pressure seat 224, the choke member 272 is moved into thereduced diameter portion 244 of the valve chamber 218 immediately abovethe high pressure fluid inlet 250 to seriously restrict further flow ofhigh pressure fluid upwardly through the valve.

body 254. Simultaneously, the fluid in the upper end of the motorcylinder 12 may leak downwardly around the upper choke member 266through the low pressure seat 224. Therefore, the action of the highpressure power fluid across the lower face of the choke member 272 willovercome all downwardly acting forces on the valve 252 and force thevalve 252 upwardly to the position shown in Fig. 10 where the ballmember 270 is seated on the high pressure seat 242. When the ball member270 becomes seated on the high pressure seat 240, the leakage of highpressure fluid will equalize the pressure above and below the chokemember 272 in a very short period of time and the choke member 272 willfall by gravity back downwardly to the position shown in Fig. 10. Itwill be understood, of course, that the harness ring 298 and cross bar296 also fall by gravity back to the position shown in Fig. 10 as soonas the piston assembly 202 starts on the up stroke.

Embodiment of Figs. 12 and 13 The modification illustrated in Figs. 12and 13 is the same as the modification illustrated in Figs. 10 and 11,except in the construction of the lower end portion of the valvemechanism 252, and in the construction of the lower end portion of thevalve chamber to accommodate the modified valve construction. Instead ofa ball-type valve member cooperating with the high pressure valve seat240, I may utilize an elongated valve element 300 having a choke portion302 on the upper end thereof of a size to fit rather loosely in thevalve seat 240. The upper end portion 304 of the element 300 above thechoke portion 302 is reduced in diameter to contact the extension 256 onthe lower end of the main valve body 254. Also, an annular seating area306 is provided on the valve element 300 immediately below the chokeportion 302 to seat on the high pressure valve seat 240.

The lower end portion 308 of the valve element 300 is reduced indiameter in downwardly spaced relation from the seating area 306 toprovide a downwardly facing shoulder 310 and to provide a sliding fit ofthe lower end of the valve element in a secondary valve chamber 312formed by a suitable insert 314 in the extreme lower end of the valvechamber 218. In this embodiment, the cross bar 296 is formed in twoparts to straddle the reduced diameter portion 308 of the valve element380 and (see Fig. 13) is connected at its opposite ends by means of bars316 to the harness ring 298. The split cross bar 296 is provided tocontact the downwardly facing shoulder 310 at the end of the down strokeof the pumping unit to unseat the valve means 252 from the low pressureseat 224 and move the choke portion 302 of the valve element 300 intothe high pressure seat 248; whereupon the high pressure fluid present atthe inlet 250 will react on the downwardly facing portion of the valveelement 308 (which is equal to the area of the portion 302 minus thecross-sectional area of the reduced portion 388 of the valve element300) and seat the valve element 300 on the high pressure seat 240.

A bore 316 extends through the length of the valve element 300 andprovides communication between the valve chamber 218 above the highpressure seat 240 and the secondary valve chamber 312 to equalize theforces acting on that portion of the cross-sectional area of the valveelement 300 represented by the cross-sectional area of the reducedportion 308. Therefore, the force required to knock the valve 252 offthe high pressure seat 240 at the upper end of the up stroke may becontrolled as desired by controlling the diameters of the valve element300. The embodiment illustrated in Figs. 12 and 13 provides a reversalof the valve 252 at the end of the up stroke in the same manner as theembodiment illustrated in Figs. and 11 and previously described.

Embodiment of Figs. 14 and 15 As previously indicated, the pump unitconstruction illustrated in Figs. 14 and 15 shows the use of a valvemechanism in the cylinder head rather than in the motor piston as in theprevious embodiments. This construction, which has been generallydesignated by reference character 350, comprises an outer jacket 352threadedly connected at its lower end to a middle plug 354 andthreadedly connected at its upper end to the upper end portion of themotor cylinder head 356. The motor cylinder head 356 has a tubularextension 358 extending downwardly therefrom into the jacket 352 toconnect with the upper end of the motor cylinder 360, which in turnextends downwardly into a counterbore 362 of the middle plug 354. Itwill be apparent that the head extension 358 and the motor cylinder 360have outer diameters less than the inner diameter of the jacket 352 toprovide an annular passageway 364 extending throughout substantially theentire length of the jacket 352. The middle plug 354 has a high pressurepower fluid inlet 366 in one side thereof which communicates with thecounterbore 362 to continuously expose the lower end portion of themotor cylinder 360 to high pressure power fluid. It will further beobserved that a plurality of ports 368 are provided in the lower endportion of the motor cylinder 360 to also direct this high pressurepower fluid into the annular passageway 364. The pump cylinder (notshown) is suitably connected to the middle plug 354 in a direction toextend vertically downward from the motor cylinder 360 and provide acomplete pumping unit suitable for use in oil wells, as previouslydescribed in connection with the other embodiments.

The motor piston 370 is tubular in form and is of a size to reciprocatein the motor cylinder 368. Suitable piston rings 372 are provided aroundthe outer periphery of the motor piston 370 to provide a sliding,sealing fit of the piston 370 in the cylinder 360. A connecting rod 374is threadedly secured to the lower end of the piston 370 and extendsdownwardly through the middle plug 354 into connection with a suitablesingle acting pump piston (not shown) disposed in the pump cylinderwhich is located below the middle plug 354. Suitable packing 376 isprovided in the middle plug 354 around the connecting rod 374 to preventleakage of the high pressure V 16 power fluid through the middle pluginto the pump cylinder. The packing 376 is suitably held in position bya follower 378 in a substantially conventional manner.

Tubular inserts 380 and 382 are secured in the tubular cylinder head 356to form an elongated valve chamber 384 which extends along the axis ofmovement of the motor piston 370 to slidingly receive the valvemechanism, generally designated by reference character 386. A highpressure valve seat 388 is secured in the cylinder head extension 358between the inserts 380 and 382, and a low pressure valve seat 390 issecured in the extension 358 below the insert 382 against a shoulder 392in the extension 358. It will also be observed that the upper end 394 ofthe upper insert 380 is closed, and both of the inserts and the valveseats are held in the desired positions in the cylinder head 356 by acap member 396 threadedly secured in the upper end of the cylinder head356.

The valve mechanism 386 comprises a main body portion 398 extendingthrough the low pressure valve seat 390 and having a head portion 400 onthe lower end thereof slidingly fitting in a bore 402 in the lower endportion of the cylinder head extension 358 in alignment with the valvechamber 384 and forming a portion of the valve chamber. An upwardlyfacing annular seating area 404 is provided on the valve head portion400 and is of a size to engage the annular seating area 406 of the lowpressure valve seat 390 when the valve mechanism is in its uppermostposition as illustrated in Fig. 15. A choke portion 408 is formed on themain body portion 398 of the valve mechanism immediately above theseating area 404 and is of a size to extend rather loosely through thelow pressure valve seat 390 in intermediate positions of the valvemechanism for controlling the application of fluid pressure on the valvemechanism and hydraulically shifting the valve mechanism, as will bedescribed. Immediately above the choke portion 408, the valve body 398is reduced in diameter to provide substantial clearance between thevalve seat 390 and the valve body when the valve mechanism is in itslowermost position as illustrated in Fig. 14. The upper end portion 410of the valve body 398 is of a size to slidingly fit in the valve chamber384 between the valve seats 388 and 390. As shown in Fig. 15, apassageway 412 is provided through the valve body 398 to providecommunication between the counterbore 402 of the cylinder extension 358and the valve chamber 384 immediately below the high pressure seat 388when the valve mechanism is in its uppermost position, for purposeswhich will be described.

The valve mechanism 386 also includes a valve body 414 above the highpressure valve seat 388 and being of a size to slidingly fit in thereduced inner diameter portion 416 of the upper insert 380 forreciprocation simultaneously with the valve body 398. A head portion 418is formed around the lower end portion of the valve body 414 and isprovided with a downwardly facing annular seating area 420 of a size tomate with the seating area 422 of the high pressure valve seat 388 whenthe valve mechanism is in its lowermost position as illustrated in Fig.14. Also, a choke portion 424 is formed immediately below the headportion 418 and is of a size to fit rather loosely in the high pressurevalve seat 388 in intermediate positions of the valve mechanism forhydraulically shifting the valve mechanism, as will be described.

An extension 426 is formed below the choke portion 424 to contact theupper end of the valve body 398 and provide simultaneous movements ofthe valve body 414 when the valve body 398 is forced longitudinally, aswill be described. It will also be observed that the extension 426 is ofa size to provide substantial clearance through the high pressure valveseat 388 when the valve mechanism is in its uppermost position asillustrated in Fig. 15. A bore 428 is extended through the valve body414 to provide constant communication between the valve. chamher 384 andthe upper portion 416 of the insert 380 to i7 6 7 reduce the pressuredifferential across the valve body 414 in substantially the samemanneras previously described in connection with the valve body 300 of thevalve mechanism illustrated in Figs. 12 and 13. The valve body 414 isconstantly urged in a downward direction by a suitable spring 430 toovercome any possibility of the valve body 414 becoming stuck in anupper and inoperative position. It will be apparent that the spring 430retains the valve body 414 in contact with the valve body 398 when thevalve mechanism is in its uppermost position, as illustrated in Fig. 15,and aids in retaining the head 418 seated on the high pressure seat 388in the lowermost position of the valve mechanism, as illustrated in Fig.14.

The valve mechanism 386 is alternately mechanically moved off of thehigh' and low pressure seats 388 and 390 at the upper and lower ends ofthe movement of the motor piston 370 by an insert 432 carried in thepiston 370, and by a trip rod 434 extending downwardly through thepiston 370 from the lower end of the lower valve body 398. The insert432 extends from a spider 436 in the motor piston 370 upwardly aroundthe trip rod 434 into proximity with the upper end of the motor piston370. The insert 432 operates to contact an extension 438 formed on thelower end of the valve body 398 near the end of the up stroke of themotor piston 370. It will be observed that the extension 438 of thevalve body 398 extends through a bore 440 in the lower end of thecylinder head extension 358 immediately below the counterbore 402 whenthe valve mechanism 386 is in its lowermost position as illustrated inFig. 14. It may also be noted that the extension 438 fits loosely in thebore 440 to provide a restriction in the flow of high pressure fluid inits movement toward the upper end of the motor cylinder 360, as will bedescribed.

As shown in Fig. 14, a sleeve 442 is slidingly carried in the upper endof the motor piston 370 and has its upper end formed parallel with thelower end face of the cylinder head extension 358 to contact theextension 358 near the end of the up stroke of the motor piston 370 andrestrict flow of fluid through the bore 440, as also will more fully bedescribed. The sleeve 442 is urged in an upward direction by a suitablecoil spring 444 and is prevented from moving out of the upper end of thepiston 370 by a suitable snap ring 446. l

The trip rod 434 is threadedly secured in the valve body extension 438and extends downwardly through the insert 432 into a counterbore 448formed in the upper end portion of the connecting rod 374. A shoulder450 is suitably formed or secured on the lower end of the trip rod 434in a position to be contacted by the spider 436 near the end of the downstroke of the motor piston 370 to mechanically move the lower valve body398 in a downward direction. It may be noted here that in thisembodiment the connecting rod 374 may be formed solid, in contrast withthe hollow connecting rod described in connection with the embodimentshown in Fig. 1.

As previously indicated, high pressure power fluid is constantly presentin the lower end portion of the motor cylinder 360 and in the annularpassageway 364 formed by the jacket 352. This high pressure power fluidis also constantly fed into the upper end portion of the valvechamber384 through ports 451 in the cylinder head extension 358 andthrough ports 452 in the upper insert 380 for control by the valvemechanism 386 which alternately directs this high pressure fluid intothe upper end of the motor cylinder 360 and closes the high pressurevalve seat 388, as will be described.

On the upstroke of the pumping unit 350, as illustrated in Fig. 14, thefluid present in the upper end portion of the motor cylinder 360 isexhausted through ports or passageways 454 formed vertically in thelower end portion of the cylinder head extension 358 into the valvechamber 384 immediately above the valve head portion 400. This fluid isthen directed through thelow pressure seat390 'and out through ports 456and 458 formed in the insert 382 and in the cylinder head extension 358,respectively, into a vertical passageway 460 extending through thecylinder head extension 358 and the cylinder head 356. The upper end ofthe passageway 460 communicates with an outlet 462 which is suitablyconnected (not shown) with the discharge from the pump end of thepresent embodiment for conduction of the exhausted power fluid to thesurface of the well, along with the well fluid being produced.

Near the end of the up stroke of the pumping unit 350, the sleeve442'carried by the piston 370 first contacts thelower face of thecylinder head extension 358 and efiectively closes oif the bore 440around the valve exf tension 438. The insert 432 then contacts the lowerend of the valve extension 438 to mechanically unseat the valve head 418from the high pressure valve seat 388. As soon as the valve head 418 isremoved from the seat 388, a portion of the high pressure power fluidleaks around the upper choke member 424 and downwardly through the bore412 of the valve body 398 into the counterbore 402 atthe lower end ofthe valve chamber. However, this high pressure power fluid is preventedfrom flowing into the upper end of the motor cylinder 360 by the sleeve442. Therefore, this high pressure fluid reacts on the lower face of thevalve head 400 to hydraulically shift the entire valve mechanism 386upwardly to the position shown in Fig. 15 where the lower valve I head400 is seated on the low pressure valve seat 390.

During upward movement of the valve mechanism 386, the choke 408 willenter the low pressure valve seat 390 prior to the time the movement ofthe piston member 370 is reversed to remove the sleeve 442 from thelower end face of the cylinder head extension 358, such that the valvehead 400 will be completely seated on ,the low pressure valve seat bythe action .of the high pressure fluid reacting on the valve and assurethat the valve 386 will not be stuck in an intermediate and inoperativeposition. It may also be noted that the bore 428 through the upper valvebody 414 provides a balancing of forces across the major portion of thearea of the upper valve body when the upper valve head 418 is seated onthe high pressure valve seat 388 to minimize the force required to knockthe valve head 418 0E of the valve seat 388.

During the down stroke of the pumping unit 350 (see Fig. 15), the highpressure power fluid is directed from the upper end portion of the valvechamber 384 downwardly through the high pressure valve seat388 aroundthe valve extension 426 and then through the bore or passageway 412through the valve body 398 into the counterbore 402 in the lower end ofcylinder head extension 358. This high pressure fluid then flows throughthe bore 440 in the lower end of the cylinder head ex-' tension 358 intothe upper end portion of the motor cylinder 360 to react on the larger,upper end of the motor piston 370 and overcome the upwardly actingpressure fluid on the valve mechanism 398. As previously described, thisaction minimizes the speed of the down stroke or return stroke of thepumping unit and minimizes possible damage of the pumping unit in gassywells. It may also be noted that 398 will be held in its uppermostposition by the action of the high pressure fluid in the counterbore402'to hydraulically hold the valve mechanism on the low valve seat 390during the complete down stroke From the foregoing it will be apparentthat the pump construction illustrated in Figs. 14 and 15 utilizessubthe valve mechanism pressure stantially the same valve mechanism asin the pump construction illustrated in Figs. 12 and 13, except that thevalve mechanism is inverted and placed in the cylinder head, rather thanin the motor piston as illustrated in Figs. 12 and 13. In each of theseembodiments the valve mechanism will be hydraulically held on itsrespective seats but may be removed from the seats with a minimum offorce. After the valve mechanism is mechanically removed from therespective valve seat, it will be automatically moved by hydraulicforces to the opposite valve seat, without fear of the valve sticking inan intermediate and inoperative position. It may also be noted that whena spring isv used above the valve mechanism, as in either the embodimentshown in Figs. 12 and 13, or the embodiment shown in Figs. 14 and 15,the valve will be shifted to its lowermost position upon stopping of thepumping unit to assure that the valve mechanism will be operative whenhigh pressure power fluid is again fed to the pumping unit. Y

Embodiment of Figs. 16 and 17 Still another embodiment of the presentinvention is illustrated in Figs. 16 and 17 wherein reference character500 generally designates a complete pumping unit comprising a motorcylinder 502 connected in tandem relation to a pump cylinder (not shown)by a middle plug 504. in substantially the same manner as illustrated inFig. 1. It will therefore be apparent that the middle plug 504 forms alower head for the motor cylinder 502 and'a suitable head 506 may bethreadedly secured on the upper end of the cylinder 502 to form theopposite head portion of the motor cylinder. In this embodiment, thetubular motor piston 508 is provided with suitable piston rings 510 inthe usual manner to provide a sealing, sliding fit of the motor pistonin the cylinder 502. Also, a tubular extension 512 extends downwardlyfrom the motor piston 508 and is threadedly secured by means of a spider514 to the upper end of a hollow connecting rod'516. The hollowconnecting rod 516 extends through suitable packing 518 in the middleplug 504 into connection with a single acting pump piston (not shown)which may be in the form of the, pump piston 36 illustrated in Fig. l. Apower fluid inlet 520 is provided in one side of the middle plug 504 tocontinuously inject high pressure power fluid into the lower portionofthe motor cylinder 502, and a fluid outlet 522 is provided in theopposite side of the middle plug 504 to discharge the exhausting powerfluid and pumped well fluid from the pumping mechanism in substantiallythe same manner as in the embodiment illustrated in Fig. l

The valve chamber 524 of the pumping unit 500 extends through the lowerportion of the piston 508, and through an insert 526 suitably secured inthe piston extension 512 against the outer portion of the spider 514. Ahigh pressure valve seat 528 is secured in the piston 508 by a suitabletubular insert 530 threadedly secured in the upper end of the piston508. It will be apparent that the insert 530 holds the high pressurevalve seat 528 against a shoulder 532 formed in the lower end portion ofthe piston 508. A low pressure valve seat 534is formed on the upper endof the spider 514, with substantial clearance being provided between thevalve seat 534 and the inner periphery of the adjacent portion oftheinsert 526.

The valve mechanism, generally designated by reference character 536,comprises a tubular valve body 538 reciprocally disposed in the valvechamber 524, and a valve sleeve 540 extending through the high pressurevalve seat 528. The upper end portion 542 of the valve body 538 isincreased in diameter to telescope over the lower end portion 544 of thevalve sleeve 540 and to provide a downwardly facing shoulder 546' on theouter periphery of the valve body. The extreme upper end 548 of thevalve body 538 is shaped to seat on the high pressure seat 528 when thevalve mechanism is in its uppermost position, as illustrated in Fig. 16. The ex- 2O treme lower end portion 550 of the valve body 538 isshaped to seat on the low pressure seat 534 when the valve mechanismis'in its lower position, as illustrated in Fig. 17.

As previously indicated, the valve sleeve 540 extends through the highpressure valve seat 528 into the upper end of the valve body 538. It mayalso be noted here that the sleeve 540 is of a length and is held in thepiston member 508 in such a position that it constantly extends into theupper end of the valve body 538 in all positions of the valve mechanism.The upper end 552 of the sleeve 540 is formed parallel with the lowerface of the upper cylinder head 506 to contact the cylinder head 506 atthe end of the up stroke of the piston 508 and restrict the flow throughthe sleeve 540, as will be described. The sleeve 540 is urged in anupward direction by a suitable spring 554 positioned around the sleevein the insert 530 and anchored between the valve seat 528 and a suitableflange 556 formed around the sleeve 540. Also, the flange 556 contactsthe upper end portion of the insert 530 in the upper position of thesleeve 540 and prevents the sleeve 540 from being removed from the upperend of the piston 508.

The valve mechanism 536 also includes a tubular choke member 558telescoped over the valve body 538 and being of a size to fit loosely inthe valve chamber 524 below the high pressure valve seat 528 forcontrolling the flow of high pressure fluid to the valve mechanism, aswill be described. The choke member 558 is actuated by a harnessassembly 560 extending downwardly around the piston extension 512 andterminating in a harness ring 562 positioned adjacent the lower end ofthe piston extension 512. It will be apparent that the upper end of theharness 560 is threadedly secured to the choke member 558 by suitablescrews 564. to'mechanically move the choke member 558 upon movement ofthe harness 560.

As previously indicated, high pressure power fluid is constantly presentat the inlet 520 in the middle plug 504 and is constantly fed into thelower end portion of the motor cylinder 502 for reaction on the lower,smaller end of the piston 508 and piston extension 512. High pressurepower fluid is also constantly fed to the medial portion of the valvechamber 524 through ports 566 in the piston extension 512 immediatelybelow the piston member 508. During the up stroke of the pumping unit500, the valve mechanism 536 is in its uppermost position with the upperend 548 of the valve body 538 in engagement with the high pressure seat528 to prevent the flow of high pressure fluid into the upper endportion of the motor cylinder 502. The fluid present in the upper endportion of the cylinder 502 is exhausted downwardly through the valvesleeve 540 and the valve body 538 into the lower end portion of theinsert 526 around the low pressure valve seat 534. At this point thefluid flows on downwardly around the valve seat 534 and through thehollow connecting rod 516 into the pump cylinder for discharge with thepumped Well fluid in the same manner as in the embodiment illustrated inFig. 1. It may also be noted that during the up stroke of the pumpingunit 500 the high pressure power fluid present in the medial portion ofthe valve chamber 524 reacts on the downwardly facing shoulder 546 tohold the valve body 538 in its uppermost position, and the spring 554holds the valve sleeve 540 in its uppermost position with the flange 556in contact with the upper end of the insert 530.

Near the end of the up stroke, the upper end 552 of the valve sleeve540' contacts the lower face of the cylinder head 506; whereupon thepiston 508 moves upwardly over the valve sleeve 540 and provides arelatively downward movement of the sleeve 540 in the piston member 503.The lower end 544 of the sleeve 540 is therefore brought into contactwith an internal shoulder 568 formed in the valve member 538 to unseatthe valve head portion 548 from the high pressure valve seat As s'oon ashigh pressure powerfluid may flow around the upper end 548 of the valvemember 538, the hydraulic forces imposed on the valve member 538 arereversed to hydraulically move the valve member 538 downwardly throughthe valve chamber 524 onto the low pressure valve seat 534. As the valvemember 538 is seated on the low pressure seat 534, the upper end 548 ofthe valve member is positioned to slightly open the small ports 570,such that high pressure fluid leaks into the valve sleeve 540 to reacton the cylinder head 506 and start urging the piston assembly down.However, the valve sleeve 540 will be removed from the cylinder head 506when the upper end of the insert 530 contacts the flange 556 and theports 57 willnthen be completely open, as shown in Fig. 17. Also, whenthe valve body 538 is seated on the low pressure valve seat 534,approximately one-half of the seating area of the lower end 550 of thevalve body will be exposed only to the lower pressure in the hollowconnecting rod 516 and the net hydraulic forces on the valve body 538will be in a downward direction to hold the valve body on the lowpressure seat during the down stroke.

During the down stroke of the pumping unit 500, the high pressure fluidflows through the inlet ports 566 and through the reduced diameter ports570, and then upwardly through the valve sleeve 540 into the upper endportion of the motor cylinder 502. This power fluid therefore reacts onthe upper, larger end of thepiston 508 and creates a net hydraulic forcein a downward direction for the down stroke. It may also be noted thatthe apertures 570 are substantially smaller in total cross-sectionalarea than the inlets ports 566 to limit the velocity of high pressurefluid flowing into the upper end portion of the motor cylinder 502,without affecting the pressure forces on the valve mechanism.

Near the end of the down stroke of the pumping unit 500, the harnessring 562 contacts an upwardly facing shoulder 572 in the middle plug 504to provide a relatively upward movement of the choke member 558 withrespect to the valve body 538 and the piston member 508. Therefore, theupper end of the choke member 558 is moved into the valve chamber 524immediately below the high pressure valve seat 528 and materiallyrestricts the flow of high pressure fluid though the ports 570.Immediately following this restriction of flow through the ports 570,ashoulder 574 formed on the inner periphery of the choke member 558contacts the downwardly facing shoulder 546 of the valve body 538 tomechanically unseat the valve body 538 from the low pressure seat 534.Immediately upon unseating of the valve body 538 from the low pressureseat 534 the pressure of the fluid in the valve body 538 and in thevalve sleeve 540 Will drop to an intermediate pressure. Thisintermediate pressure is also present above the upper end of thevalvebody 538 by reason of the ports 570, and high pressure fluid reactson the shoulder 546 of the valve body 538 to produce a net hydraulicforce on the valve body 538 in an upward direction to shift the valvebody 538 upwardly against the high pressure seat 548.

When the valve body 538 is in engagement with high pressure seat 528,the piston member 508 will be urged upwardly and the choke member 558and harness 560 will move back downwardly to a lower position, asillustrated in Fig. 16, by the action of gravity. As previouslydescribed, the fluid present in the upper end of the motor cylinder 502is exhausted downwardly through the valve sleeve 540, valve member 538,and hollow connecting rod 516 into the pump cylinder to provide a nethydraulic force on the piston member 508 in an upward direction.

The pumping unit 500 illustrated in Figs. 16 and 17 provides a. valvemechanism which directs the flow of the high pressure fluid to and fromthe larger end of the motor piston through the valve mechanism tominimize the required size of the piston assembly and valve mechanism,such that the maximum capacity of the motor end of the unit may berealized. It may be noted, however, that the valve mechanism 536 ismechanically unseatedfrom the high and low pressure seats and is thenhydraulically shifted to an opposite seat by action of choking members,along the same lines as the embodiment shown in Fig. 1. In this regardit may be observed that the lower end portion 544 of the valve sleeve540 acts as a choking member in shifting the valve mechanism to the lowpres- .sure seat after the valve mechanism has been mechanicallyunseated from the high pressure seat.

From the foregoing it will be apparent that the present inventionprovides a novel fluid operated pumping unit which may be operated asslow as desired and yet may be operated through a substantial speedrange. The unit utilizes a single valve mechanism which will be thrownat the opposite ends of the piston movement by a minute physicalmovement of the piston to minimize a possibility of the valve becominglocked in an inoperative position. The present invention also provides ameans for controlling the speed of the return stroke of the unit in theform of an orifice in the passageway leading to the larger end of thedifferential area motor piston assembly, whereby increases in operatingfluid pressure will have a minimum eifect on the speed of the. returnstroke. It will be further apparent that the valve will be moved to oneof the seats of the motor unit, such as the high pressure seat whichprovides a power stroke of the pump, unless the valve is on an oppositeseat or is just completing a power stroke, thereby minimizing thepossibility of the valve assuming an inoperative position when thepumping unit is shut down for any period of time. v

Changes may be made in the combination and arrangement of parts asheretofore set forth in thespecification and shown in the drawings, itbeing understood that changes may be made in the precise embodimentsshown without departing from the spirit and scope of the invention asdefined in the following claims.

I.claim: I

.1. In a fluid operated pump unit including a single acting pumpoperated by a reciprocating .fluid motor having a motor piston and amotor cylinder and a fluid passageway through the motor piston having -avalve way upstream of the valve means, and means supporting said sleevefor movement to contact and unseat the valve means at the end of thepower stroke of the pumping unit.

2. In a fluid operated pumping unit as defined in claim 1 characterizedfurther in that said sleeve movement is arranged to contact the end ofthe motor cylinder at the end of the power stroke and momentarilyrestrict the flow of high pressure fluid downstream of the valve.

3. A fluid operated pumping unit, comprising a fluid motor, a singleacting pump connnected to and operated by the motor, said motorcomprising a motor cylinder, a differential area piston reciprocallydisposed in the cylinder and having the smaller end thereof continuouslyexposed to high pressure power' fluid, a piston type valve havingopposed seating areas and reciprocally disposed in a valve chamber inthe piston on an axis parallel with the axis of the piston, a firstpassageway in the piston intersecting one end portion of the valvechamber and arranged to direct high pressure fluid to the larger end ofthe piston for a return stroke of the pumping unit, a second passagewayin the piston intersecting the opposite end portion of the valve chamberand arranged to exhaust fluid from the larger end of the piston for apower stroke of the pumping unit, opposed seats in the valve chamberaround the first and second passageways to alternately receive the valveand close the passageways, a sleeve slidingly secured in. the firstpassageway between the valve chamber and the larger end of the piston toform an orifice in the first passageway and control the velocity of highpressure fluid flow through the first passageway, said sleeve being of alength to contact the respective end of the motor cylinder near the endof the power stroke and unseat the valve from the seat associated withthe first passageway for exposing the respective end of the valve tohigh pressure power fluid which moves the valve to the opposite seat,'and means for moving the valve in the opposite direction at the end ofthe return stroke of the unit.

4. A fluid operated pumping unit as defined in claim 3 characterizedfurther in that the valve has an extension on the end thereof associatedwith the first passageway of a size to extend through the respectiveseat when the valve is adjacent to the seat, the clearance between theextension and the respective seat being greater than the clearancebetween the outer periphery of the sleeve and the inner periphery of therespective portion of the first passageway in which the sleeve ispositioned, and the outer end of the sleeve being formed parallel withthe respective end of the motor cylinder, whereby high pressure powerfluid escapes past said extension faster than past the end of the sleeveand around the sleeve, when the sleeve contacts the respective end ofthe motor cylinder and unseats the valve, for hydraulically shifting thevalve to the opposite seat immediately upon unseating the valve from theseat around the first passageway.

5. A fluid operated pumping unit as defined in claim 3 characterizedfurther in that the valve is extended through the seat associated withthe second passageway to form a head portion slidingly disposed in asecondary valve chamber in the motor piston, the end of the secondaryvalve chamber remote from the seat around the second passageway being incommunication with the smaller end of the motor piston to continuallyexpose the respective end of said head portion to high pressure powerfluid and urge the valve toward the seat around the first passageway,the respective pressure areas of the valve and head portion beingdistributed to provide a'net hydraulic force on the valve to move thevalve to the seat around the first passageway when the valve is ofl theseat around the second passageway, and means for unseating the valvefrom the seat around the second passageway at the end of the returnstroke of the pumping unit.

6. A fluid operated pumping unit, comprising a fluid motor, a singleacting pump connected to and operated by the motor, said motorcomprising a motor cylinder, a differential area piston reciprocallydisposed in the cylinder and having the smaller end thereof continuouslyexposed to high pressure power fluid, a piston type valve having opposedseating areas andreciprocally disposed in a valve chamber in the pistonon an axis parallel with the axis of the piston, a first passageway inthe piston intersecting one end portion of the valve chamber andarranged to direct high pressure fluid to the larger end of the pistonfor a return stroke of the pumping unit, a second passageway in thepiston intersecting the opposite end portion of the valve chamber andarranged to exhaust fluid from the larger end of the piston for a powerstroke of the pumping unit, opposed seats in the valve chamber aroundthe first and second passageways to alternately receive the valve andclose the passageways, an extension on each end of the valve of a sizeto extend into the respective seat in intermediate positions of thevalve, yet the valve is of a size such that each extension will beremoved from its respective seat when the valve is seated on theopposite seat, a head portion extending outwardly from the valveextension associated with the seat around the second passageway andslidingly disposed in a secondary valve chamber in the piston, the endof the secondary valve chamber opposite the seat around the secondpassageway being in communciat1on with the smaller end of the motorpiston to continuously expose the respective end of said head portion tohigh pressure power fluid and continuously urge the valve toward theseat around the first passageway, and means for unseating the valve atthe ends of the power and return strokes of the pumping unit.

7. A pumping unitas defined in claim 6 characterized further in that thecross-sectional area of said head portion is greater than thecross-sectional area of the main body portion of the valve less thecross-sectional area of the valve extension associated with the seataround the first passageway to provide a net hydraulic force on thevalve tending to move the valve to the seat around the first passagewaywhen the valve is unseated from the seat around the second passageway.

8. A pumpingunit as defined in claim 6 characterized further in thatsaid means comprises a sleeve slidingly disposed in the first passagewaydownstream of the respective valve seat and being of a length to extendbeyond thetlarger end of the motor piston to contact the respective endof the motor cylinder at the end of the power stroke, whereby the sleevemoves into the motor piston and unseats the valve from the seat aroundthe first passageway, and a harness slidingly secured to the smaller endof the motor piston and extending into the secondary' valve chamber forcontacting the respective end of the motor cylinder and the head portionat the end of the return stroke for unseating the valve from the seataround the second passageway.

9. A pumping unit as defined in claim 8 characterized further in thatsaid sleeve is of a size to provide an orifice in the first passagewayfor controlling the velocity of high pressure fluid flow to the largerend of the motor piston.

10. A fluid operated motor comprising a cylinder, a differential areapiston reciprocally disposed in the cylinder and having the smaller endthereof continuously exposed to high pressure power fluid, a piston typevalve having opposed seating areas and reciprocally disposed in a valvechamber in the piston on an axis parallel with the axis of the piston, afirst passageway in the piston intersecting one end portion of the valvechamber and arranged to direct high pressure fluid to the larger end ofthe piston, a second passageway in the piston intersecting the oppositeend portion of the valve chamber and arranged to exhaust fluid from thelarger end of the piston, opposed seats in the valve chamber around thefirst and second passageways to alternately receive the valve and closethe passageways, a sleeve slidingly securedv in the first passagewaybetween the valve chamber and the larger end of the piston to formanorifice in the first passageway and control the velocity of highpressure fluid flow through the first passageway, said sleeve being of*a length to contact the respective end of the motor cylinder near theend of one stroke of the motor and unseat the valve from the seatassociated with the first passageway for exposing the respective end ofthe valve to high pressure power fluid which moves the valve to theopposite seat, and means for moving the valve in the opposite directionat the end of the opposite stroke of the motor.

11. A fluid operated motor as defined in claim 10 characterized furtherin that the valve has an extension on the end thereof associated withthe first passageway of a size to extend through the respective seatwhen the valve is adjacent to the seat, the clearance between theextension and the respective seat being greater than the clearancebetween the outer periphery of the sleeve and the inner periphery of,the respective portion of the first passageway in which the sleeve ispositioned, and the outer end of the sleeve being formed parallel withthe respective end of, the motor cylinder, whereby-high pres- .25, .4sure power fluid escapes past said extension faster than past the end ofthe sleeve and around the sleeve, when the sleeve contacts therespective end ofthe motor cylinder and unseats the valve, forhydraulically shifting the valve to the opposite seat immediately uponunseating the valve from the seat around the first passageway.

12. A fluid operated motor as. defined in claim characterized further inthat the valve is extended through the seat associated with the secondpassageway to form a head portion slidingly disposed in a secondaryvalve chamber in the motor piston, the end of the secondary valvechamber remote from the seat around the second passageway being incommunication with the smaller end of the motor piston to continuallyexpose the respective end of said head portion to high pressure powerfluid and urge the valve toward the seat around the first passageway,the respective pressure areas of the valve and head portion beingdistributed to provide a net hydraulic force on the valve to move thevalve to the seat around the first passageway when the valve is off theseat around the second passageway, and means for unseating the valve-firom the seat around the second passageway at the end of said oppositestroke of the motor.

13. A fluid operated motor comprising a cylinder, a differential areapiston reciprocally disposed in a cylinder and having the smaller endthereof continuouslyexposed to high pressure power fluid, a piston typevalve having opposed seating areas and reciprocally disposed in a valvechamber in the piston on an axis parallel with the axis of the piston, afirst passageway in the piston intersecting one end portion of the valvechamber and arranged to direct high pressure fluid to the larger end ofthe piston, a second passageway in the piston intersecting the oppositeend portion of the valve chamber and arranged to exhaust fluid from thelarger end of the piston, opposed seats in the valve chamber around thefirst and second passageways to alternately receive the valve and closethe passageways, an extension on each end of the valve of a size toextend into the respective seat in intermediate positions of the valve,yet the valve is of a size such that each extension will be removed fromits respective seat when the valve is seated on the opposite seat, ahead portion extending outwardly from the valve extension associatedwith the seat around the second passageway and slidingly disposed in asecondary valve chamber in the piston, the end of the secondary valvechamber opposite the seat around the second passageway being incommunication with the smaller end of the motor piston to continuouslyexpose the respective end of said head portion to high pressure powerfluid and'continuously urge the valve toward the seat around the firstpassageway, and means for unseating the valve at the ends of the powerand return strokes of the pumping unit.

14. A motor as defined in claim 13 characterized further in that thecross-sectional area of said head portion is greater than thecross-sectional area of the main body portion of the valve less thecross-sectional area of the valve extension associated with the seataround the first passageway to provide a net hydraulic force on thevalve tending to move the valve to the seat around the first passagewaywhen the valve is unseated from the seat around the second passageway.

15. A motor as defined in claim 13 characterized further in that saidmeans comprises a sleeve slidingly disposed in the first passagewaydownstream of the respective valve seat and being of a length to extendbeyond the larger end of the motor piston to contact the respective endof the motor cylinder at the end of one stroke of the motor, whereby thesleeve moves into the motor piston and unseats the valve from the seataround the first passageway, and a harness slidingly secured to thesmaller end of the motor piston and extending into the secondary valvechamber for contacting the respective end of the motor cylinder and, thehead portionatthe end of the opposite stroke of the motor for unseatingthe valve from i the seat around the second passageway.

16. A motor as defined in claim 15 characterized further in that saidsleeve is of a size to provide an orifice in the first passageway forcontrolling the velocity of high pressure fluid flow to the larger endof the motor piston.

l7.'A reciprocating type fluid motor, comprising: a cylinder member; apiston member reciprocally disposed in the cylinder member and having alarge end and a small end; a supply of high pressure power fluid; meansproviding constant communication between said supply and the small endof the piston member to constantly apply power fluid against said smallend and urge the piston member in one direction in the cylinder member,a valve chamber in one of said members; a first passageway intersectingthe valve chamber providing communication between said supply and thelarge end of the piston member to direct power fluid against the largeend of the piston member and urge the piston member in an oppositedirection; an exhaust passageway intersecting the valve chamber andcommunicating with the large end of the piston member for exhaustingpower fluid from the end portion of the cylinder member associated withthe large end of the piston member and provide movement of the pistonmember in said one direction; a valve seat in the valve chamberassociated with each of the first and exhaust passageways, said valveseats being positioned in spaced relation; valve means reciprocallydisposed in the valve chamber for alternately closing said valve seatsand controlling the flow of power fluid to and from the large end of thepiston member; and valve actuating means carried by the piston memberphysically engaging the valve means near the end of the movement of thepiston member in either direction, to unseat the valve means from thevalve seat associated with the respective passageway closed by the valvemeans during movement of the piston member in the respective direction;said valve means including choke means controlling the flow of fluidthrough the valve chamber in intermediate positions of the valve meansfor hydraulically shifting the valve means into a closed position withrespect to either seat when the valve means has been unseated from theother seat by the valve actuating means.

18. A motor as defined in claim 17 wherein said valve means includes anelongated body portion having a bore extending longitudinallytherethrough, said body portion being arranged to position said bore incommunication with one of said passageways when the seat associated withthe respective passageway is opened.

19. A motor as defined in claim 17 wherein one of said I valve actuatingmeans includes a sleeve slidingly carried by the piston member andprotruding from the large end of the piston member arranged to contactthe respective end of the cylinder member and restrict flow through saidfirst passageway.

20. A motor as defined in claim 17 wherein the crosssectional area ofsaid first passageway downstream of said valve means is less than onehalf the cross-sectional area thereof upstream of said valve means.

21. A motor as defined in claim 17 wherein said valve chamber and saidfirst and exhaust passageways are in the piston member.

22. A motor as defined in claim 17 wherein said valve chamber and saidfirst and exhaust passageways are in the cylinder member.

23. A reciprocating type fluid motor, comprising: a cylinder member; apiston member reciprocally disposed in the cylinder member and having alarge end and a small end; a supply of high pressure power fluid; meansproviding constant communication between said supply and the small endof the piston member to constantly apply power fluid against said smallend and urge the piston member in one direction in the cylinder member;a valve chamber in one of said members; a first passageway intersectingthe valve chamber providing communication between said supply and thelarge end of the piston

